The present invention pertains to slide gate valves, and particularly to a method of casting an integral slide gate and nozzle assembly for such a valve. More specifically, it comprises a method wherein a casing conforming to the exterior sides and bottom of the assembly is placed upside down on a flat smooth plate to form a mold, a tube conforming to the channel to be formed in the assembly is placed within the casing and refractory castable material is placed within the mold.
Slide gate valves are devices whereby the flow of molten metal such as steel from a ladle or tundish or other container is controlled by sliding or rotating a plate having an orifice into and out of alignment with a similar opening in the molten metal containing vessel. Such devices are shown, for example, in U.S. Pat. No. Re. 27,237. It is common to place a collector nozzle below the sliding plate and in alignment with the opening in the plate to guide the stream of molten metal in a single unit, for example as shown in U.S. Pat. Nos. 3,731,912 and 3,841,539.
Commonly, these units are made by forming, for example by pressing and firing, separate slide gate plates and collector nozzles, and assembling a slide plate and a nozzle in a metal casing, for example by embedding them in mortar in the casing. However, in order to obtain adequate flatness in such units, it has been necessary to grind their top surfaces after assembly. On the other hand, it is known to form an integral assembly comprising both the sliding plate and the dependent nozzle by casting refractory concrete into a metal casing, such unit not requiring grinding if the top surface of the valve is cast against a smooth surface.
One problem with such casting method of forming these assemblies is that the refractory castable used must be of sufficiently high quality that it will resist the action of molten steel. However, only the top surface and interior of the channel through the plate and nozzle are in contact with molten steel. Accordingly, the refractory castable used in the remainder of the structure is of higher quality, and consequently more expensive, than is needed.
The present invention offers a method of casting such assemblies which have a high grade refractory castable on the upper surface of the plate and along the metal flow channel through the plate and nozzle and a lower grade refractory in other portions of the assembly.